Outcomes And Ventricular Dyssynchrony In Patients With Right Ventricular Apical Pacing And Preliminary Results After Replacement With Alternative Right Ventricular Site Pacing

PartⅠNew-onset Heart Failure after Permanent Right Ventricular Apical Pacing in Patients with Acquired High-grade Atrioventricular BlockIntroduction:Emerging data have suggested that right ventricular(RV)apical pacing results in progressive left ventricular(LV)dysfunction and contributes to the development of heart failure(HF).This study aimed to investigate the prevalence and clinical predictors for the development of new-onset HF after long-term RV apical pacing in patients with acquired atrioventricular(AV)block who require permanent pacing.Methods:We retrospectively studied the clinical outcomes after long-term RV apical pacing for acquired AV block in 304 patients without a prior history of HF.All the atients had>90%ventricular pacing as determined by device diagnostic data. Results:After a median follow-up of 7.8 years,79 patients(26.0%)had developed new-onset HF after RV apical pacing.Univariate Cox-regression analysis revealed that an old age at the time of pacemaker implantation(P<0.001),the presence of coronary artery disease(P<0.001),atrial fibrillation(P=0.03),VVI pacing(P<0.001), wide paced QRS duration(P<0.001),and new-onset myocardial infarction(P<0.001) were predictors for HF.Multivariate analysis revealed that older age at implantation (Hazard ratio[HR]1.06,95%confidential interval[CI]1.04-1.09,P<0.001),the presence of coronary artery disease(HR 1.98,95%CI 1.12-3.50,P<0.05)and a wider paced QRS duration(HR 1.27 for each 10ms increment,95%CI 1.11-1.45,P<0.001) were independent predictors of HF.Furthermore,cardiovascular mortality was significantly increased in those with HF(36.7 vs.2.7%,P<0.001).Conclusions:After a median follow-up of 7.8 years,permanent RV apical pacing was associated with HF in 26%of patients.Elderly age at the time of implant,a wider paced QRS duration and the presence of coronary heart disease independently predicted new-onset HF.More importantly,HF after RV apical pacing was associated with a higher cardiovascular mortality.PartⅡPrevalence of Ventricular Dyssynchrony in Patients with High Degree Atrioventricular Block after Permanent Right Ventricular Apical PacingBackground:The detrimental effects of chronic right ventricular(RV)apical pacing on cardiac function are considered possibly related with ventricular dyssynchrony. However,some patients tolerate RV apical pacing well during long-term follow-up. We assumed that the degrees of ventrieular dyssynchrony are different among individual patients.Several studies have revealed that paced QRS duration was a risk factor of heart failure after RV apical pacing,but the relation between paced QRS duration and the degree of ventricular dyssynchrony has not been clearly characterised. The aim of this study is to investigate the prevalence of ventricular dyssynchrony and its related factors in patients with chronic RV apical pacing.Methods:Echocardiography including tissue Doppler image(TDI)was performed in 75 patients with high degree atrioventricular block after an average of 9.1 years' RV apical pacing.All patients had >90%ventricular pacing as determined by device diagnostic data.Left ventricular(LV)ejection fraction was calculated from the apical 2- and 4-chamber images with biplane Simpson's method Interventricular dyssynchrony was calculated as the difference between pulmonary pre-ejection interval(PPEI)and aortic pre-ejection interval(APEI),which is named interventricular mechanical delay(IVMD).An IVMD≥40 ms was used as a cutoff value for interventricular dyssynchrony.Myocardial TDI parameters were measured off-line.Ts was defined as the time interval between the onset of QRS wave to the peak systolic velocity during ejection phase.The time delay between peak systolic velocity at basal lateral and septal segments[Ts-(lateral-septal)]was calculated. Significant intra-LV dyssynchrony was defined as Ts-(lateral-septal)≥60ms.In addition,Ts-SD was calculated using 6-basal and 6-mid-segrnental model.Ventricular dyssynchrony was judged when Ts-(lateral-septal)was≥60ms and/or IVMD was≥40 ms.Paced QRS duration was measured from the 12 lead standard surface ECG.Results:The mean IVMD was 38±20(range:4-120)ms,and Ts-(lateral-septal)44±37(range:0-139)ms.Thirty patients(40%)had interventricular dyssynchrony,and 28 patients(37%)had significant intra-LV dyssynchrony.Ten patients(13%)had both interventricular and intra-LV dyssynchrony.Totally forty-eight patients(64%)had either intra- or interventricular dyssynchrony,or both.Patients with dyssynchrony were younger than those without dyssynchrony.There were no significant differences in gender,concomitant cardiovascular diseases and mean duration of pacing between patients with or without significant ventricular dyssynchrony.Correlation analysis showed there was significant but weak association between paced QRS duration and IVMD(r = 0.286,P=0.013)or Ts-SD(r = 0.302,P=0.009),but there was no correlation between paced QRS duration and Ts-(lateral-septal)(r = 0.136,P=0.245). There was significant negative relation between paced QRS duration and LV ejection fraction(r= -0.447,P<0.001).Conclusions:Significant ventricular dyssynchrony existed in 2/3 of patients with acquired high degree atrioventricular block after permanent RV apical pacing.There is significant but weak correlation between paced QRS duration and the degree of ventricular dyssynchrony.PartⅢEffects of Right Ventricular Outflow Tract / Septal Pacing in Patients with Prior Right Ventricular Apical PacingIntroduction:Since fight ventricular apical(RVA)pacing was associated with an increased risk of developing heart failure,alternative ventricular pacing sites have been investigated in the recent decade.Right ventricular outflow tract(RVOT)or right ventricular septal(RVS)pacing has been shown to be superior to RVA pacing in preserving left ventricular(LV)function among newly-implanted pacing patients. However,whether RVS pacing could reverse the deleterious effects of RVA pacing remains unclear.Methods:Twenty-four patients with previous permanent RVA pacing were admitted for pacemaker replacement because of battery exhaustion.All patients had a ventricular pacing percentage≥95%.Patients were randomly assigned to be replaced with RVOT / RVS pacing(RVOT/S group,n=12)or continue RVA pacing(RVA group, n=12).Echocardiography including tissue Doppler imaging(TDI)was performed before and 6-12 months after pacemaker replacement.TDI from apical 4,2 and 3 chamber views were acquired and analyzed offline.Ts-SD was calculated using 6-basal and 6-mid-segmental model to evaluate intra-LV dyssynchrony. Interventricular dyssynchrony was calculated as the difference between pulmonary pre-ejection interval(PPEI)and aortic pre-ejection interval(APEI),which is also named interventricular mechanical delay(IVMD).LV ejection fraction(LVEF)was calculated from the apical 2- and 4-chamber images with biplane Simpson's method Paced QRS duration was measured from the 12 lead standard surface ECG.Six minute hall walk(6MHW)was performed to evaluate patients' functional capacity.Results:After a mean of 10.4 months,in RVOT/S group,the mean paced QRS duration decreased significantly from 169±10 ms to 158±8 ms(P=0.002),LVEF increased from 0.55±0.06 to 0.57±0.07(P=0.01),Ts-SD from 36.9±17.0 ms to 29.8±20.2 ms(P=0.08),IVMD from 34.6±15.4 ms to 21.4±14.3 ms(P=0.20),and the distance of 6MHW changed from 331±103 m to 366±119 m(P=0.12),compared with the baseline.While in RVA group,all the parameters hadn't changed significantly.Conclusions:RVOT / RVS pacing shortened paced QRS duration,tended to improve intra-LV mechanical dyssynchrony,and improved LV systolic function in patients with prior chronic RVA pacing.